Generally, an acrylic acid may be obtained by a gas phase catalytic oxidation reaction of one or more selected from propane, propylene, isobutylene, and acrolein.
For example, under the presence of an appropriate catalyst in a reactor, propylene or propane is converted through acrolein into the acrylic acid, and at a rear part of the reactor, the mixed gas that includes the acrylic acid, unreacted propylene or propane, acrolein, an inert gas, carbon dioxide, a steam and various reaction organic byproducts is obtained.
Generally, the mixed gas is cooled or contacted with water in an absorbing column to dissolve soluble components such as the acrylic acid in the mixed gas to obtain the aqueous solution including the acrylic acid, and to discharge nonsoluble gas in the mixed gas to the upper part of the absorbing column to recycle the gas to the reactor or convert the gas through an incineration furnace into harmless gas for discharging.
The acrylic acid aqueous solution is provided through a stripping column into a azeotropic distillation column, the acrylic acid among the acrylic acid aqueous solution that is provided into the azeotropic distillation column is obtained in a high concentration of acrylic acid at a lower part of the column of the azeotropic distillation column. In addition, water and the organic byproduct among the acrylic acid aqueous solution that forms the azeotrope in conjunction with an appropriate azeotropic agent in the azeotropic distillation column is discharged to the upper part of the column of the azeotropic distillation column to be recycled into the acrylic acid absorbing column or wasted.
Generally, according to the type of azeotropic agent that is used in the azeotropic distillation column, the separation method of the azeotropic agent, the operation method of the separation column at a rear part of the water separation process, and the treatment method of water separated in the azeotropic distillation column are significantly changed.
For example, Japanese Unexamined Patent Application Publication No. 1997-157213 discloses a method of directly providing a water layer obtained in an azeotropic distillation column into an acrylic acid absorbing column without a solvent recovery column to obtain an acrylic acid aqueous solution. Here, the waste water that is generated in the azeotropic distillation column and includes 0.5-5.0% by weight of the acrylic acid, 3-10% by weight of the acetic acid, and 0.01-0.5% by weight of the distillation solvent is recycled into the acrylic acid absorbing column to highly efficiently absorb the acrylic acid.